Conceptual (semantic) knowledge is an essential component of language and thinking. The breakdown of this complex system in many common neurological and psychiatric disorders, including stroke, dementia, temporal lobe epilepsy, and schizophrenia, has a devastating impact on quality of life. Understanding how this information is organized, represented in the brain, and affected by neuropathology is a major focus of research. In the last two decades, there has been a resurgence of interest in theories that suggest a close tie between perceptual-motor experience and language. These theories suggest that conceptual knowledge is embodied, or directly relies on, sensory-motor systems. Such theories are controversial because they contrast with the older view that concepts are abstract, amodal, and symbolic, and implemented outside the brain's sensory-motor systems. Embodied theories of conceptual knowledge raise several fundamental questions: (1) What is the nature of the association between sensory-motor systems and concepts? Which components of the sensory-motor systems are involved, and in processing which types of knowledge? (2) Is the relationship between conceptual and perception/action systems limited to association, or is it essential? Are sensory-motor systems necessary for conceptual processing, or are they activated (as seen in recent neuroimaging studies) only because they are highly associated with concepts? Answering these questions has critical implications not only for understanding the nature of this vital system, but also for developing a deeper understanding of the deficits experienced by patients with conceptual impairments, a critical step in developing informed and effective rehabilitation therapies. The proposed research will examine the role of sensory-motor systems in conceptual processing in both the healthy and the impaired brain, using state-of-the-art methods including functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), and behavioral studies of intact and brain-injured populations. The first three specific aims are concerned with elucidating the extent to which sensory-motor systems are implicated in language processing, testing predictions derived from stronger and weaker versions of the Embodiment theory. Aims 4 and 5 address the issue of centrality, providing strong tests of the extent to which sensory-motor information is required for comprehending relevant expressions. The specific aims are: (1) to study the role of sensory-motor experience and perspective in conceptual processing, (2) study the relationship between sensory-motor systems and abstract language, (3) to examine the conceptual representation of space and time, (4) to study the effects of sensory-motor TMS on conceptual representations, and (5) to study conceptual knowledge in patients with motor system pathology.